1. Field of the Invention
The present invention relates to a lightfast colorant and a lightfast ink composition including the same, and more particularly, to a lightfast colorant that is derived by chemically binding a cinnamate derivative to the molecular structure of a conventional colorant and a lightfast ink composition comprising the same.
2. Description of the Related Art
Ink-jet printing, which is a kind of non-impact printing, has the advantages of low noise generation, compared to impact printing, and effective color printing realization, compared to laser beam printing.
There are two types of non-impact printing: continuous ink-jet printing and drop-on-demand (DOD) printing. In continuous ink-jet printing, while ink is continuously discharged, a change in an electromagnetic field is induced to control a direction in which the ink is jetted. DOD printing, in which micro droplets of ink are jetted, includes thermal-bubble ink-jet printing and piezoelectric ink-jet printing. In thermal-bubble ink-jet printing, ink is discharged by a pressure generated by the swelling of bubbles that are generated as the ink is heated. In piezoelectric ink-jet printing, ink is discharged by a pressure generated by using a piezoelectric plate that is deformed mechanically by electricity.
Recently, a dot-size of ink-jet printers has become smaller and there has been an increasing need for high-resolution, high-quality prints. Smaller dot-size ink-jet printers require a head having smaller nozzle orifices. However, smaller nozzle orifices may become clogged by precipitates, and thus, affect the size of the ink droplets and a performance of the printer. Clearly, the composition of the ink affects the clogging of the nozzle orifices. For this reason, a wetting agent is commonly added to ink-jet ink compositions.
An ink composition for ink-jet printing basically comprises a colorant, a solvent, and an additive. A dye or a pigment may be used as the colorant. However, the use of a dye as the colorant is limited because the dye imparts an inferior lightfast property to a print. When a pigment is used as the colorant, a resulting print is more lightfast than when a dye is used, but the print is still subject to a color change or discoloration when exposed to ultraviolet (UV) light. An additional lightfastness enhancer may be used. However, negative side effects, for example, the clogging of the nozzle orifices by agglomerated ink, the formation of a heterogeneous ink composition, and the like, occur when the light-fastness enhancer is used.